The present invention relates to a working vehicle suitable for a turf grass management working vehicle used for work such as fertilizing, chemicals spraying, lawn mowing and the like in golf courses.
In the golf courses and parks, the working vehicle, also called turf grass management working vehicle, is used to grow turf grass. With such vehicles, various types of works such as the fertilizing, spreading topdressing, the spraying chemicals, aerating soil by injecting air, or clearing tree leaves by using a blower are conducted. The various types of works are carried out with attachments, appropriate for the types of works, mounted on a bed of the working vehicle.
Recently, a working vehicle with an automatic transmission is on the increase from viewpoints of a smoothly starting, comfortable traveling performance, and an easy driving operation. Such vehicle with the automatic transmission has travel modes such as xe2x80x9cParking (P)xe2x80x9d, xe2x80x9cRear Drive (R)xe2x80x9d, xe2x80x9cNeutral (N)xe2x80x9d and xe2x80x9cDrive (D)xe2x80x9d, which are appropriately selected with a shift lever by a driver. A shift from a vehicle start to a maximum speed thereof is carried out only by an operation of accelerator through selecting the Drive mode, i.e., a position (D) of the shift lever.
However, the Drive mode has the following problems. That is, although a shift control under the Drive mode sufficently acts on a flat road, that on a slope is not always sufficient, for example, there are some problems in a climb-up performance of a heavy vehicle or an engine-brake peformance when climbing down a slope. In other words, at a stage os starting to climb up a slope, a transmission ratio is relatively low in geleral, and so vehicle speed during the climb-up is apt to become low. Then, a kick down for increasing the transmisison ratio often occurs by an operation of a driver, thereby there exists a problem that a travel stability of the working vehicle may be lost. Also, when climbing down the slope, the transmission ratio lowers as the vehicle speed of the working vehicle increases, thereby lowering the performance of the engine brake. As a result, there exists a problem that a foot brake must be operated in order to reduce the vehicle speed, which may cause injury of turf grass.
In particular, when spraying the chemicals, a vehicle weight may be over 2,000 kg under the condition in which a tank is filled with chemicals, wherein if the function of engine brake is weak at the climb-down stage, the friver can not avoid using the foot brake since it is difficult to control the vehicle speed. However, if the foot brake is depressed hard in order to supplement a brake force, there is a danger that wheels may be locked to injure turf grass.
In particular, when spraying the chemicals, a vehicle weight may be over 2,000 kg under the condition in which a tank is filled with chemicals, wherein if the function of engine break is weak at the climb-down stage, the driver can not avoid using the foot break since it is difficult to control the vehicle speed. However, if the foot break is depressed hard in order to supplement a break force, there is a danger that wheels may be locked to injure turf grass.
An object of the present invention is to provide a working vehicle with an increased climb-up performance at a stage of climbing up a slope and an increased engine-brake force at a stage of climbing down a slope so as to improve travel stability thereof and also keep a good condition of turf grass.
Furthermore, another object of the present invention is to provide the working vehicle in which the climb-up performance and the engine-brake force at the stage of climb-down is automatically controlled, thereby enabling the vehicle to be driven only by an operation of an accelerator at any place without a manual operation of transmission.
The working vehicle of the present invention has a working machine and comprises an engine, an automatic transmission for transmitting a power of the engine to wheels, and control means for controlling a transmission ratio of the automatic transmission unique to a climb-up mode or a climb-down mode when the control means determines that the working vehicle is in the climb-up mode or the climb-down mode.
According to the present invention, the working vehicle can climb up a slope maintaining the engine speed even at a stage of climbing up the slope since the transmission ratio on the slope is controlled with the transmission ratio unique to the climb-up mode, thereby enabling the climbing-up traveling to be stable. Further, when climbing down the slope also, the working vehicle is controlled with the transmission ratio unique to the climb-down mode, so that a stable engine brake force can be obtained. Consequently, not only increase of vehicle speed at a stage of climbing down, but also injury of turf grass due to a quick operation of a foot-brake device can be prevented. In other words, the safety at a time of climbing down can be improved.
According to the working vehicle of the present invention, the control means may be arranged to control the transmission ratio of the automatic transmission at a maximum value when it is determined that the working vehicle is in the climb-up mode or the climb-down mode.
In accordance with the present invention, the working vehicle can climb up the slope with high engine speed, and climb down with a large engine-break force.
Further, according to the working vehicle of the present invention, the control means may be arranged to control the transmission ratio of the automatic transmission through a normal control table when determining that the working vehicle is in a normal travel mode, and through a climb-up control table or a climb-down control table when determining that the working vehicle is in a climb-up mode or a climb-down mode, respectively.
Also, preferably, the control means determines that the working vehicle is in either the climb-up mode or the climb-down mode when the control means detects that a shift lever is changed over to a predetermined position.
Further, preferably, the control means determines that the working vehicle is in the climb-up mode when an accelerator opening is at or above a predetermined value, and an acceleration of the working vehicle is at or below a predetermined value.
Moreover, the control means determines that the working vehicle is in the climb-down mode when an accelerator opening is at or below the predetermined value, and an acceleration of the working vehicle is at or above the predetermined value.
In accordance with the present invention, since just the already existing data showing the driving condition of vehicle are employed for determining a travel mode, no addition of parts for determination of the climb-up or down mode is needed.
In addition, preferably, the control means determines that the working vehicle is in either the climb-up mode or the climb-down mode when an absolute value of an inclined angle of the working vehicle as detected by an inclination sensor is at or above a predetermined value.
In accordance with the present invention, since the inclination sensor directly detects the inclined amount of vehicle to control the transmission ratio, the working vehicle can automatically and quickly conduct a changeover to the climb-up or climb-down mode without influence of unsteady accelerator operation by an operator.
The automatic transmission of the present invention may be a continuously variable transmission, thereby enabling the shift control to be smoothly and steplessly conducted.